When a fluid flows along a surface, irrespective of whether the flow is laminar or turbulent, the particles in the vicinity of the surface are slowed down by virtue of viscous forces. The fluid particles adjacent to the surface stick to it and have zero velocity relative to the surface. Other fluid particles attempting to slide over them are retarded as a result of an interaction between faster and slower moving fluid. The effects of the viscous forces originating at the surface from the non-moving fluid extend into the body of fluid, but a short distance from the surface the velocity of the fluid particles approaches that of an undisturbed free stream. The fluid contained in the region of substantial velocity change is called the boundary layer. Given a typical heat exchanger tube with a moving fluid as a coolant, the phenomena of a boundary layer significantly affects the efficiency of the heat transfer between the moving fluid and the tube. Unlike moving fluid which transfers heat through convection and conduction, the boundary layer portion against the surface essentially is a layer of non-moving fluid directly against the wall of the tube which allows heat transfer only through conduction. Furthermore, laminar fluid flow which may exist in the tube creates a thicker boundary layer of relatively stagnant fluid than does turbulent flow. Consequently, in order to maximize the heat transfer efficiency between a tube and the enclosed cooling fluid, absent other factors an ideal situation would involve complete turbulence of the moving fluid throughout the length of the heat exchanger tube. An additional advantage of turbulent flow, aside from the reduction of the boundary layer thickness, is that the fluid is mixed by the turbulence. This promotes a more uniform fluid temperature distribution throughout the tube and this, in itself, is conducive to better heat transfer.
This phenomena of deliberately creating a turbulent coolant flow within a heat exchanger tube has been known in the art for quite some time and the devices used to create the turbulent flow have been numerous. Typically, each of the devices used in the past required installation at the time the heat exchanging device was fabricated or required substantial modifications for the installation after the heat exchange device was fabricated. A device is needed for installation within heat exchanger tubes that will effectively create turbulent flow of the moving fluid but also be easily installed and, if necessary, easily removed.
It is an object of this invention to provide a device suitable for creating a turbulent fluid flow within a tube having a moving fluid. It is further object of this invention to provide a turbulence generating device that may be easily inserted and removed from a tube. It is a further object of this invention to provide a turbulence generating device that may be inserted and secured within a tube using no permanent connections. It is a further object of this invention to provide a turbulence generating device that is of relatively simple design such that fabrication and production is relatively inexpensive.